New vinyl polymer and process for its production



Patented June 19, 1945 UNITED STATE NEWVINYL s, PATENT canoe POLYMER ANDrnocrzss roa rrs raonnc'rron Merlin Martin Brubaker, Wilmington, lleL,as-

signor to E. Wilmington, Del.,

No Drawing.

I. du Pont de Nemours & Company,

a corporation of Delaware Application November 16, 1940, Serial No.365,943-

screams. (green-+19 F I objects will be apparent from theiollowingdescription of the invention.

These and other objects appearing hereinafter are accomplished bysubjecting a polyvinyl thiol ester to hydrolysis, thus producing apolyvinyl thiol.

The following example sets forth'a certain well defined instance of theapplication of this invention. It is, however, not to be considered alimitation'thereof since many modifications may be made withoutdeparting from the spirit and scope of this invention.

Example I Fifteen parts by weight of polyvinyl thiol acetate wassuspended in 200 parts by weight of a sodium hydroxide solution inmethanol and this suspension was allowed to stand at room temperatureuntil the polymer went into solution. This required about 3 days. Theresulting solution was then acidified with acetic acid to give someconditions alumina may be used to catalyze the hydrolysis. Neitheracids'nor alumina are as convenient for hydrolysis, however, as thealkali metal or alkaline earth metal hydroxides because the polyvinylthiol precipitates as it is formed when the acidic or weakly alkalinemedia a gelatinous precipitate which could be redissolved in alkali andreprecipitated by means 01 acid. The reprecipitated material wascarefully washed and dried. in the absence of oxygen, to give anamorphous solid which was infusible and in.- soluble in water andorganic. solvents but soluble in alkali. The product was analyzed forsulfur and found to contain 52.96%; 52.83%. The calculated sulfurcontent of polyvinyl thiolis 53.34%.

In place of sodium hydroxide alkali or alkaline earth metal hydroxidesmay be used to catalyze the hydrolysis of the polyvinyl esters.Alternatively, hydrolysis maybe carried out with an acid, particularly amineral acid such as hydrochloric acid.

When alkali or alkaline earth metal hydroxides are used to hydrolyze thepolyvinyl thiol esters.

' the hydroxide is preferably used in the ratio of about 2 to 10 molsper vinyl thiol ester unit present. If less is used, the hydroxide isneutralized by the acid formed and the hydrolysis becomes very slow.When the hydrolysis is carriedout in the presence of acid, the amount ofcatalyst em ployed may conveniently be from 1 to 10% on the weight ofthe vinyl thiol ester present. Under are employed.

Methanol is a convenient solvent for sodium or potassium hydroxides, butother solvents may be used. It is also possible to dissolve thepolyvinyl thiol ester in a solvent such as acetone, dioxane, etc., andadd the required amount of catalyst to the solution. The concentrationof catalyst or of polymer may be varied widely but it is most convenientto use from 5 to 25% solutions.

'More dilute solutions waste solvent, and morev concentrated solutionsmake the removal of byproducts more difficult.

When an alkaline catalyst in alcohol is used, the polyvinyl thiol formedgoes into solution as the sodium salt and must be precipitated with anacidic reagent. Any convenient acidic reagent such'a's acetic acid,formic acid, hydrochloric acid, sulfuric acid, etc., may be used as theprecipitant.

The precipitated polyvinyl thiol must be washed if the hydrolysisby-products are to be completely removed. In many cases ,this isconviently done by agitation and centrifugation with successivequantities of water or alcohol. Since the polyvinyl thiol is solubleonly in alkali, any nonalkaline solvent which will dissolve'the acid andthe salt formed in the hydrolysis may be used. Hydrolysis may beaccelerated by using elevated temperatures, but temperatures above 30 to40 C. cause some discoloration of the polymer, particularly in thepresence of strong alkalis. Acidic solutions may conveniently berefluxed. The time required to complete the hydrolysis will depend uponthe temperature at which the reaction is carried out, being shorter forhigher temperatures.

During the hydrolysis, washing. and drying of polyvinyl thiol it isdesirable to keep an inert atmosphere over the polymer so as to avoiddegradation through oxidation.

Polyvinyl thiol may be obtained from any of its esters by hydrolysis.The preparation of such esters is fully disclosed in my copendingapplication Serial No. 269,075, filed April 21, 1939. It is generallypreferred to prepare the vinyl thiol esters by pyrolysis ofZ-mercaptoethanol esters of monoand di-carboxylic acids. Examples ofsuitable car boxylio acids are propionic, butyric, valeric,chloroacetic, lactic, benzoic, toluic, naphthoic, furoic, andquinolinic. The esters may be readily prepared by any method well knownto acid, acid halide or anhydride on 2-mercaptoethanol by standardprocedures.

The best temperatures for carrying out the pyrolysis depend to someextent upon the particular ester used and also upon suchiactors as thenature of the reaction vessel and rate of passage of the ester'throughthe reaction vessel. Generally, temperatures in the range of 300 to 700C. may be employed but it is preferred to operate in the range of 450 to500 C. The process may be operated as a continuous operation, in whichcase the vinyl thiol ester is separated from the reaction'product andthe unconverted ester recycled. The pressure need not be atmospheric,but in the case of the higher esters it may be desirable to use reducedpressures, and in the case of lower esters it may be better to usepressures greater than atmospheric. It is generally preferred topyrolyze in the presence of a carrier material such as carbon dioxide,nitrogen, or acetic acid.

The monomeric vinyl thiol esters obtained by pyrolysis may then bepolymerized to the polymeric esters. This may be accomplished bycarrying out the polymerization reaction in the presence of apolymerization catalyst such as bonzoyl peroxide, boron trifiuoride,hydrogen peroxide, urea peroxide, lauroyl peroxide, succinic peroxide orthe like. The polymerization reaction may also be carried out in theabsence of a catalyst or in the presence of such catalysts as metalhalides such as ferric chloride, zinc chloride, copper chloride, calciumchloride, etc. Temperatures used for the polymerization may range fromroom'tenrnerature to 120 Q.

The vinyl thiol ester may be interpolymerized with a polymerizableorganic compound having the radical in which one of the bonds issatisfied by hydrogen or a monovalent hydrocarbon radical and the othervalence by halogen, ether oxygen or sulfur or a radical containing acovalent carbon atom which is separated from the vinyl or vinylidenecarbon by not more than one chain atom. Examples of suitable compoundsare vinyl chloride, vinyl acetate, acrylic and methacrylic acids andtheir esters; e. g., methyl, ethyl, propyl, octyl, dodecyl, etc,styrene; chloro-2-butadiene-1,3; butadiene-i,3; vinyl succinimide; vinylphthalimide, etc. Other compounds which may be interpolymerized,however, are allyl aluminate, dimethally] borate, etc.

When the hydrolysis reaction is carried out on interpolymerizationproducts an interpolymer of polyvinyl thiol is obtained.

Polyvinyl thiol may ,be oxidized by air or oxygen or other oxidizingagents as shown by the following examples.

Example II Fifty parts of an alkaline methanol solution containing about1.8 parts of poly vinyl thiol was put in a flask and oxygen bubbled intothe mixture at room temperature for about 15 minutes. Agelatlnousmaterial was formed very quickly. It was filtered oif, washed carefullywith water, and allowed to dry. The product was infusible and insolublein alkali. This material was a polyvinyl disulflde made by the oxidationof polyvinyl thiol.

Stronger oxidations of polyvinyl thiol gives polyvinyl sulfonic acid asshown below.

Example III Ten parts of polyvinyl disulnde was treated with an excessof 60% nitric acid at about 50 C. for 2 hours. After the disulflde hadall dissolved, additional water was added, and the nitric acid was thenremoved by steam distillation in vacuum. This treatment was repeated andthe product finally evaporated in a vacuum desiccator for several days.The product was a sticky, slightly yellow mass which was highlyhygroscopic and insoluble in organic solvents.

Example IV The process of Example 111 was repeated using milderoxidation conditions. A product was obtained which could be precipitatedfrom a corn centrated aqueous solution by the addition oi alcohol. Thisproduct was an amorphous white powder which had a sapcniflcationequivalent oi 857, whereas the calculated value was 108, indicating thatonly a small part of the sulfur had been oxidized to a sulfonic acid inthis example. The product of the stronger oxidation reaction 01 ExampleIII was, or course, oxidized to a greater extent.

Example V Eighty-four parts of polyvinyl thiol acetate was treateddirectly with 800 parts of nitric acid.

The reaction was fairly vigorous and the reaction mixture was cooledwith ice. The reacti n was over in about an hour and the mixture thenheated at C. for hour. The excess nitric acid was removed bydistillation in vacuum and the polyvinyl sulionic acid obtained asbefore Strong oxidation of inter-polymers containing polyvinyl thiol orpolyvinyl thiol acetate may be used to prepare an interpolymercontaining polyvinyl sulfonic acid.

Polyvinyl thiol is of use primarily as an insolubilizing agent in otherresins. In application the polyvinyl thiol is thoroughly mixed with afilm forming resin or material as a phenol-formaldehyde orurea-formaldehyde resin, or drying oil-polyhydrlc alcohoi=poiycarboxylicacid resin, or cellulose derivative, etc. and the resulting mixtureformed into a film, tube, ribbon, or shaped article. The product thusprepared when exposed to atmospheric c.. gen will oxidize to a hard,insoluble, iniusible solid.

Polyvinyl thiol is also of use as an insoiubilizing material ininterpolymers; thus, the vinyl thiol ester may be interpolymerlzed insome other material, the interpolymer hydrolyzed, and formed into afilm, tube, ribbon, or shaped article and the product oxidized to renderit hard and inert to the common reagents.

It is apparent that many widely difit'erent embodiments of thisinvention may be made without departing from the scope and spiritthereoi and therefore it is not intended to be limitec except asindicated in the appended claims.

I claim:

1. The process which comprises subjecting s polyvinyl thiol ester tohydrolysis.

2. The process which comprises reacting a polyvinyl thiol ester withalkali present in an amount suflicient to hydrolyze the polyvinyl thiolester acidifying the resulting product, and recovering a polyvinylthiol.

' 3. The process in accordance with claim 2 characterized in that thepolyvinyl thiol ester i: polyvinyl thiol acetate.

4. The process which comprises subjecting a weasel v i I 3 'polyvinyithiol cater to hydrolysis in the presence 6. A polyvlnyl thioh or anacid whereby polyvinyl thiol is obtained. I 7. An interpolymer of thehypothetic vinyl 5. The process which comprises subjecting an thiol witha. polymerizable organic compound interpolymerization product of a vinylthiol ester having the radical with a polymerizable organic compoundhaving 5 the radical n,c -c

, I v MERLIN MARTIN BRUBAKER.

to hydrolysis.

